Fractional separation of fatty oil substances



y t. 28, 1948. w. P. cal-:E

.FRACTIONAL SEPARATION 0F FATTY OIL SUBSTANCES 2 Sheets-Sheet 1 FiledApril 5, 1947 Sept. 28, 1948. w. P. GEE

FRCTIONAL SEPARATION OF FATTY OIL SUBSTANCES Filed April 5, 1947 2Sheets-Sheet 2 INVENTOR.

W L. z, /AM P GEE ATT RNEY Patented Sept. 28, 1948 FRACTIONAL SEPARATIONF FATTY OIL SUBSTANCES william P. Gee, Plainfield, N. J., assigner aTexaco Development Corporation, New York, N. Y., a corporation ofDelaware Application April 5, 1941, serial No. '139,541

9 claims. (ci. 26o-428.5)

This invention relates to the fractional separation of fatty oilsubstances such as the fatty oil mixtures derived from vegetable, landand marine animal or other sources.

Such oils usually comprise fatty acids having from about 12 to 18 carbonatoms per molecule and, in the natural state, are largely in the form ofglycerides, although they frequently include the free fatty acids. Insome instances, as for example, in the case of sperm oil, the fattyacids are largely combined as esters of the higher aliphatic alcoholsalthough they may be present as glycerides to the extent of 12 to 30% ofthe fatty oil.

This invention is a continuation-in-part of my copending application S.N. 615,886 filed September 12, 1945, now abandoned which in turn is acontinuation in part of my application S. N. 454,- 666 filed August 13,1942. The present invention involves separation of fatty substancescontained in the fatty oil, into fractions of different melting point ordifferent solidification point range by continuous filtration in thepresence of a polar solvent liquid such as acetone, methylethyl ketone,benzene, di and tri-chlorethylenes, nitrparaiiins such as nitroethane,and non-polar solvents such as low boiling petroleum hydrocarbons,namely propane, butane, pentane, etc, or compatible mixtures of any ofthese solvents. The fatty substance to be treated may be any particularpor-tion of a raw oil, such as a mixture consisting essentially of freefatty acids obtained by acidulation of the saponified acids separatedfrom the oil.

The term fatty substance as used herein is intended to mean the fattyacids, whether occurring naturally or synthetically or derived fromnatural products by conventional procedures; the glycerides of the fattyacids, most frequently the triglycerides, but also the equivalent monoor diglycerides and mix-tures thereof; and the other esters of the fattyacids, that is to say esters with either the lower aliphatic alcoholssuch as the ethyl and methyl esters through the complete range includingesters of fatty acids and long chain aliphatic alcohols such as cetylpalmitate and the like. The term fatty acids includes not only thetypical saturated and unsaturated members having from about 12 to 18carbon atoms, but also the known fatty acids having a greater number -ofcarbon atoms, as well as the shorter chain fatty acids down to abouteight carbon atoms. The present invention permits fractional separationof the foregoing from each other whether in relatively pure mixtures orin admixture with other and non-saponiable mate- Y for example, beoperated at a lower temperature A level. In this wayvthe original fattyoil feed may be separated into a series of separate, substanvrials whichmay sometimes occur in the fatty oil substances and mixtures .referredto above.

The solvent liquids contemplated are organic solvents from which thefatty substances may be crystallized without alteration in theiressential state.

The fatty oil substance to be filtered is mixed with the solvent liquidin an amount and under conditions of temperature such as to obtain amixture composed of a liquid phase comprisingfatty oil substancedissolved in solvent liquid and a solid phase consisting essentially offatty constituents of predetermined and relatively narrow melting pointor solidiflcation point range. This phase mixture with the solid phasedispersed substan-tially uniformly throughout the liquid phase is passedin a continuous stream to a continuous filter advantageously of therotating leaf or drum type wherein the filter surface passes through ytially pure fractions.

An important feature of the invention involves maintaining the properrelation between the solid and liquid phases in the phase mixturepassing to the filter. It is advantageous that the volume of such liquidphase bein the ratio of about 16 to 50 volumes per unit volume of solidphase. Expressed in terms 'of percent solids it is desirable Athat thesolids lcontained in the phase mixture passing to the filter be intherange about 2% to 6% by volume of the phase mixture and notsubstantially in excess of this value.

Optimum results, within this range, are obtained when the solids ln thephase mixture are about 5 to 6% of the volume of the phase mixture.

If the solid phase is rpresent inthe feed mixture to a larger extentthan this a filter cake is obtained which is too thick to permiteffective displacement of liquid phase from the filter cake during thewashing step and under such circum- 'stances sharp separation betweencomponent fractions of the fatty oil feed is not realized.

The ratio of solid phase to liquid phase can be controlled Ibycorrelating the amount and character of the solvent liquid employed withthe temfperature at which the Imixture is filteredand also by recyclingeither filtrate or solids 'to the mixture passing to the filter.Recycling of filtrate increases the ratio of liquid to solids and isadvantageous from the standpoint of exerting a beneficial modifyingaction on the crystalline structure of the solid phase whereby moreeflicient filtration and more c1ose-cut fractionation may be realized.On the other hand, solids may be recycled so as to maintain Ithe solidcontent witihin the aforesaid 2 to 6% of the feed mixture, particularlywhere the solvent content in the liquid phase cannot be reduced withoutan excessive increase in the viscosi-ty of the liquid phase.

As already intimated liquid p'hase retained in the filter cake isdisplaced by washing' prior to discharge from the filter. This washingis accomplished =by applying a further quantity of the solvent liquid tothe filter cake, in situ, in such manner as 4to displace the retainedliquid phase as filtrate. Effective displacement is secured by applying.the wash solvent liquid to the filter cake in the form of an unbrokenfilm or -sheet of solvent liquid maintained over the cake for a periodof time subsequent lto its emergence from the filtering mixture. Tofacilitate realizing complete displacement of' retained liquor thefilter cake should not exceed about one-quarter inch in thickness. Onlthe other hand, the cake should be not less than about one-eighth inchin thi-ckness; otherwise difficulty is encountered in discharging itfrom the filter surface.

An important advantage of the present invention is that it provides acontinuous method of effecting fractional separation of these fattysubstances, such separation heretofore Ihaving been effected ybypressing, usually involving a succession of pressing operations appliedto the same fraction.

A further advantage is that the present invention permits realizing asharper lseparation between individual fractions of the feed oil.

For example, when treating an oil derived from soya bean and consistingessentially of free fatty acids. in orde-r to separate therefrom afraction consisting essentially of .palmit-ic and stearic acids, inaccordance with lthe process of this invention, a filter cake isobtained in a. single ltering operation which, after removal of :thesolvent, will have an iodine number of 5 or less indicating thesubstantial absence of the unsaturated acids which are of lower meltingpoint. By prior art methods involving pressing, about the best that canbe expected is a product having an iodine number of about 15.

In order to describe the invention further reference will now be made tothe figures of the accompanying drawing.

As indicated in Figure 1, fatty oil from a source not shown is conductedthrough a pipe to a mixer 2 while solvent from a source not shown isconducted through a pipe 3 to the mixer. The solvent may be, forexample, a low molecular weight ketone such as acetone or methylethylketone or a mix-ture of such ketones with benzol or other aromatichydrocarbons. 'llhe solvent may be mixed with the fatty oil in theproportion of about 2 to 5 parts of solvent to 1 part by volume of fattyoil although the actual proportions used will depend upon the characterof the fatty oil feed and also upon the degree of fractionation desired.

'I'he resulting mixture may be conducted from the mixer 2 to a heater lwherein the mixture is warmed or heated sufficiently to effect completesolution of the fatty oil in the solvent liquid. If

desired, the mixture may -be raised to a tempera- -ture A25 to 50 F.Yabove the temperature of oomplete solution in order to condition themixture.

The solution is then passed from the heater I to a chiller or cooler 5wherein the temperature of the solution is reduced to the desired pointso as to effect crystallization of the constituent of the fractiondesired to be separated. A solid phase is obtained containing fatty oilconstituents of predetermined melting point or solidioation Ipointrange.

If desired, only a portion of the total solvent liquid may be mixedinitially with the fatty oil and this partially diluted mix-ture chilledto approximately the filtering temperature, the remainder of the solventliquid prechilled to the filtering temperature being added -to thepartially diluted mixture prior to filtration. l

In any case, the mixture brought to the desired filtering temperature ispassed to a filter 6 advantageously -comprising a hollow rotatingcylinder or hollow rotatin-g leaves covered with filter cloth with meansfor creating vacuum within the interior of the filter element or forexerting positive pressure upon the exterior thereof.

The liquid phase is separated from the feed mixture as filtrate which isdischarged through a pipe l to a receiver 8, while the solid phase isretained on the filter cloth as a filter cake and discharged from thefilter through a conduit 9 rto a receiver III.

As will be explained later, the filter cake is washed in situ withadditional solvent liquid which m-ay be introduced to the filter throughthe pipe I I. The resulting wash filtrate is usually removed from thefilter as a separate stream through a pipe I2 discharging into areceiver I3. This wash filtrate is advantageously used for mixing withfresh fatty oil feed to the system.

The interior of the filter 6 is maintained at approximately the sametemperature as that of the entering feed mixture. This is accomplishedby circulating gas through the filter. Thus, an inert gas such as fluegas is drawn from a storage tank I4 by means of a blower I5 and passedthrough a heat exchanger I6 wherein the gas is brought to the desiredtemperature. From the heat exchanger I6 the gas is passed through a pipeI1 into the hood of the filter 6 and is discharged from the interior ofthe lter through the filtrate discharge pipes 1 and I2. The dischargedgas is removed from the receivers 8 and I3 and may be returned to thesuction side of the blower I5 as indicated.

If necessary the circulating gas may be scrubbed with a suitable liquidmedium to remove moisture. Moreover, the scrubbing medium may also servein the capacity of a cooling agent when it is desired to reduce thetemperature of the gas.

The filtrate drawn of from the receiver 8 may be discharged through apipe 2li leading to a solvent recovery unit 2l. This unit may comprise astill and other auxiliary apparatus adapted for stripping the solventliquid from the fatty oil.

On the other hand, the filtrate may be conducted through a pipe 22 to a.succeeding stage ent solvent or in the presence of the same solvent fbut in different proportion so as to effect precipitation of anotherfraction consisting of constituents of the fatty oil feed.

As indicated, a portion of the filtrate may be recycled through a pipe23 to theL feed mixture. The recycled material may be mixed with thefeed after passage of the feed through the chilling system. or may bemixed therewith at any other point, as for example with the feedentering the mixer 2, or with the stream entering the heater l.

The filter cake discharged into the receiver I may be drawn off througha pipe 24 to a solvent recovery unit 25 substantially similar to theunit 2I wherein solvent liquid is recovered from the fatty oil products.

Figure 2 shows diagrammatically and in outline a rotary vacuumcontinuous filter of the type used in Figure 1 with the filtering cycleindicated thereon. The filter surface is shown at 50 and is divided bydivision strips 5I into a plurality of longitudinal segments about theperiphery of the filter. The customary filter valve which controls theapplication of suction and the supply of pressure blowback gas to theinterior of the filtering segments at various stages in the cycle ofrotation of the filter is indicated at 52.

Numeral 53 indicates the liquid level of the mixture within the filterbowl. This liquid level may be such as to provide from about 40 to 50%submergence of the filter drum. y

The filter drum rotates in the direction of the arrow 5I and cakeformation starts at 55. At this point the filter valve opens tocommunicate suction to the filtering surface, which suction continuesthroughout the extent of the immersed portion of the filter to providethe pick up" or cake forming area 56.

The filtrate from this section isr discharged through the filtrate lineas previously described. As the filter segments consecutively emergefrom the filtering mixture their communication with filtering outlet iscut oil' at 58; and after a short rotation, communication with thewashing and drying discharge port of the valve is initiated at 59. Theaction of the vacuum then creates a pressure differential on thefiltering surface which causes a chilled gaseous atmosphere surroundingthe filter to act upon the cake during the drying stage 60 to drain orstrip retained liquid phase from the cake. The washing of the drainedcake then commences as indicated at 5 I The wash solvent liquid isintroduced to a Weir trough or pipe 62 which is mounted to extendlongitudinally throughout the length of the filter, being supported inany suitable manner corresponding approximately to the zenith ofrotation of the filter drum. Wash solvent is continuously supplied tothe Weir through the previously mentioned pipe I I so as to maintain acontinuous overflow at the Weir 53. Additional wash solvent may also besupplied to the cake by means of sprays. Hence an unbroken sheet or filmof wash liquid is caused to flow over the filter cake in a directionopposite to the direction of the filter rotation. -Suflicient washliquid is supplied so as to maintain this thin liqud film over theexposed portion of the filter cake substantially throughout the extentof the washing zone indicated at 65.

The pressure differential existing upon opposite sides of the cake andliquid film causes the wash liquid to ow into the cake and displaceremaintity of wash liquid supplied and the extent of the washing zone issuch as to obtain substantially complete displacement of retained liquidfatty oil solution from the filter cake.

Following the washing zone the cake is sub- Jected to further pressuredifferential during the drying stage 58 at which time cold gas from theatmosphere surrounding the filter and supplied from the previouslymentioned heat exchanger I5 is drawn through the filtering surface todisplace Wash solvent as well as to maintain the filtering surface atapproximately the same temperature as the feed mixture entering thefilter from the previously mentioned chiller 5.

The liquids and gases drawn through the filter during passage from 59 to81, at which latter point the discharge passage is closed by the valve,are discharged through the wash filtrate pipe I2.

A full block 8B separates the termination of the vacuum and initiationof the pressure blowback at 69. At this point chilled gas under pressureis discharged through the passage in the valve to the interior of thesegments of' the filter causing a slight distention and movement of thefilter cloth indicated at 10. This assisted by the scraper 'II serves toremove the formed and dried filter cake.

The reverse flow of chilled gas or blowback terminates at l2 and thefull block indicated at 13 separates the termination of the cakedischarge zone from the beginning of the cake forming zone at 55whereupon the cycle is repeated.

Operation of the invention will now be described by reference to thefollowing example in which an acidulated soya bean oil having an APIgravity of 25.4, titer test of about 70 F. and iodine number (Wijs) ofabout 135 is subjected to successive filtrations.

One volume of oil is mixed with between 2 and 3 parts of acetone and theresulting mixture chilled at a rate of about 1.5 to 2 F. per minute to atemperature level of about 0 to plus 5 F. thereby crystallizing outsolids consisting essentially of the saturated acids, stearic andpalmitic.

After or during chilling suiiicent filtrate from the subsequent primaryfiltering operation is added to the mixture in order that the solidcontent is adjusted to permit formation of not more than a one-quarterinch cake Within the cake forming time on the continuous filter whenallowing suiiicient time to supply the amount of wash solvents specifiedbelow. Under this condition, which is most important for successfuloperation of the process, the mixture is passed to a continuous rotaryfilter as described in connection with Figures 1 and 2 so as to separatethe liquid phase as filtrate and the solid phase as filter cake. Thefilter cake is washed in situ with additional acetone, chilled to about0 to plus 5 F. temperature, in the proportion of about 1.5 to 2 volumesof wash solvent per volume of fatty oil charged to the filter.

The filter cake discharged from the filter and after removal of thesolvent -liquid amounts to 'about 10.0% by volume of fatty oil feed andis characterized by having a titer of about F. and an iodine number of'about 3.

The filtrate on the basis of being free from solvent will thus amount toabout 90.0% by volume of the initial charge oil and is characterized byhaving a titer of about 24 F. and an iodine value of about 150.

A portion of the filtrate is recycled to control per cent of solids aspreviously described. The remainder of the filtrate, without removal ofsolvent, is then passed to a second stage wherein it is chilled to atemperature of about minus 35 to minus 45 F. following the sameprocedure as previously described. In this operation a second filtercake amounting to about 41% by weight of the original fatty oil feedisobtained. It will consist essentially of oleic acid and ischaracterized by having a titer of about 65 F. and an iodine number of70. The second filtrate on the basis of being solvent free will thusamount to about 49% of the original fatty oil feed and will consist ofoil having a titer in the range minus 4 to plus 3 F. and having aniodine value in the range 164 to 170. Recycling of filtrate may also benecessary to control per cent solids in the feed to the second stagefiltration.

While the first filter cake and filtrate and also the second precipitatehave been described as having specific values for titer and iodinenumber nevertheless it is contemplated that the operation may beregulated so as to produce fractions having tests varying somewhat fromthose specified. For example, the'filter cake produced in the firstfiltration may consist of fatty oil material having a titer in the range115 to 125 F. and an iodine number in the range to 25; while thefiltrate produced in the initial filtration may contain oil having atiter in the range to 24 F. and an iodine number in the range 140 to160.

Likewise the filter cake produced in the second filtration may have atiter in the range 59 to 95 F. and an iodine number in the range 50 to100.

The solidication point or titer of the fatty oil substances comprisingthe filter cake is materially affected by the presence of small amountsof either lower or higher melting point constituents of the fatty oil,particularly in view of the fact that mixed fatty acids apparently formeutectic mixtures in which the melting point of the mixture of any twoacids may be considerably lower than the melting points of theindividual acids. For example, the mixture of palmitic and stearic acidsobtained in the lter cake from the first filtration described in theabove example may have a, melting point of about 125 F. whereas themelting points of palmitic and stearic acids are about 145 to 157 F.respectively.

Accordingly, it is important to realize effective displacement washingof the filter cake prior to discharge from the filter and for thisadditional reason it is desirable to form on the filter a filter cakewhich is susceptible to effective washing in situ. As mentioned earlierthe forming of such cake is dependent upon controlling the ratio ofsolids to liquids in the liquid and solid phase mixture passing to thefilter. One method of adjusting this ratio is by recycling of filtrateas previously disclosed. In some instances the recycled filtrate mayamount to as much as 2 to 3 volumes per volume of fatty oil feed to theprocess.

Although soya bean oil has been referred to in the foregoing example,nevertheless it is contemplated that the procedure of this invention isapplicable to treatment of other vegetable and animal oils includingcorn oil, palm oil, cocoanut oil, rape oil, walnut oil and sardine oil.The process may be Aapplied to the crude oil or to any desired portionthereof. As previously intimated the crude oil or a fraction thereof maybe saponified by treatment with caustic. the resulting saponified acidconstituents separated, and thereafter treated with mineral acid so asto obtain a free fatty acid mixture. The free fatty acid mixture may besubjected to fractionation by the process of the present invention.Alternately essentially free fatty acids may be obtained by the wellknown pressure splitting of fats.

It may be applied to fatty acid mixtures prepared from any source as bythe oxidation of paraffin hydrocarbons, an example of which would be theproducts obtained by oxidizing petroleum wax.V

Obviously many modifications and variations of the invention ashereinbefore set forth may be made without departing from the spirit andscope thereof and therefore only such limitations should be imposed asare indicated in the appended claims.

I claim:

1. In the separation of solidifiable constituents from fatty substancescontained in fatty oil by continuous vacuum filtration in the presenceof a solvent liquid from which solidifiable constituents can becrystallized .without substantial alteration in their essential state,said filtration involving forming, washing, drying on and dischargingfrom a rotating drum filter surface a filter cake of solids in acontinuous recurring cycle, the steps comprising chilling said fattysubstance mixed with a solvent comprising aliphatic ketone to afiltering temperature lat which crystallization of def siredsolidifiable constituents occurs, forming at said filtering temperaturea chilled mixture comprising a liquid phase of noncrystallized fattyconstituents dissolved in solvent and a solid 'phase of crystallizedfatty constituents, said solid phase amounting to from about 2 to not inexcess of about 6% by volume of the liquid phase at said filteringtemperature, passing a stream of said mixed phases, the solid phasebeing uniformly dispersed throughout the liquid phase, to a continuousrotary vacuum drum filter with the filter drum about 40 to 50% submergedin the filtering mixture, separating liquid phase as filtrate andforming a filter cake of solid phase. washing said filter cake in situto displace retained liquid phase, continuously discharging filtratefrom said filter, and continuously discharging washed filter cake fromthe filter substantially free from fatty constituents solidifying belowand above said filtering temperature,

2. In the separation of saturated fatty acids from a mixture ofsaturated and unsaturated fatty acids having from about 12 to 18 carbonatoms per molecule by continuous vacuum filtration in the presence of asolvent liquid, said filtration involving forming, washing, drying onand discharging from a rotating drum filter surface a filter cake orsolids in a continuous recurring cycle, the steps comprising chillingsaid fatty acid feed mixed with a solvent comprising an aliphatic ketoneto a'filtering temperature at which crystallization of desiredsolidifiable constituents occurs, forming at said filtering temperaturea mixture comprising a liquid phase of saturated fatty acids dissolvedin solvent and a solid phase of crystallized saturated acids, said solidphase amounting to from .about 2% to not in excess of about 6% by volumeof the liquid phase at said filtering temperature, passing a stream ofsaid phase mixture, the solid phase being uniformly dispersed throughoutthe liquid phase, to a continuous rotary vacuum filter with the filterdrum about 40 to 50% submerged in the filtering mixture, separatingliquid phase as filtrate and forming a filter cake of solid phase,continuously discharging flltrate from said filter and continuouslydischarging the washed filter cake -comprising saturated acidsubstantially free from unsaturated acids.

3. The method according to claim 2 in which the solvent comprises a lowmolecular weight aliphatic ketone and the filtration is eected at atemperature of about F.

4. In the separation of solidiiiable constituents from a fatty oilmixture by continuous vacuum filtration in the presence of a solventliquid, said filtration involving forming, washing, drying on anddischarging from a rotating drum filter surface a lter cake of solids ina continuous recurring cycle, the steps comprising mixing soybean fattyacids with from about 3 to 5 .volumes of a low molecular weight ketone,heating the mixture to effect complete solution of oil in the solvent,chilling the solution to a filtering temperature in the region of about0 F. so as to form a mixture of fatty oil and solvent comprising aliquid phase of fatty oil dissolved in the solvent and a solidA phaseconsisting essentially of stearicv and palmitic acids, said solid phaseamounting to about 2 to 6% by volume of the liquid phase at saidfiltering temperature, passing a stream of said mixed phases, the solidphase being uniformly dispersed throughout the liquid phase, to acontinuous rotary vacuum drum filter with the filter drum about 40 to50% submerged in the filtering mixture, separating liquid phase asfiltrate and forming a filter cake of solid phase, washing said filtercake in situ with additional solvent at about said filtering temperatureto displace retained liquid phase, continuously discharging filtratefrom said filter and continuously discharging Washed filter cake fromthe filter substantially free from fatty oil constituents other thansaid stearic and palmitic acids.

5. In the separation of solidifiable constituents from a fatty oilmixture by continuous vacuum filtration in the presence of a solventliquid, said filtration involving forming, washing, drying on anddischarging from a rotating drum filter surface a filter cake of solidsin a continuous recurring cycle, the steps comprising mixing soybeanfatty acid with about 4 volumes of acetone, heating the mixture to eectcomplete solution of oil in the solvent, chilling the solution to afiltering temperature in the region of about 0 F.

so as to form a mixture of fatty oil and solvent comprising liquid phaseof fatty oil dissolved in the solvent and a solid phase consistingessentially of stearic and palmitic acids, said solid phase amounting toabout 2 to 6% by volume of the liquid phase at said filteringtemperature, passing a stream of said mixed phases, the solid phasebeing uniformly dispersed throughout the liquid phase, to a continuousrotary vacuum drum filter with the filter drum about 40 to 50% submergedin the filtering mixture, separating liquid phase as filtrate andforming a filter cake of solid phase, washing said filter cake in situwith additional acetone at about said filtering temperature in theproportion of about ll/l to 2 volume of acetone per volume of soy-beanoil charged to the filter to displace retained liquid phase,continuously discharging filtrate from said filter and continuouslydischarging washed filter cake from the filter substantially free fromfatty oil constituents other than said stearic and palmitic acids` 6. Inthe separation of solidiiiable constituents from a mixture of fattysubstances contained in fatty oil by continuous vacuum filtration in thepresence of a solvent liquid from which solidifiable constituents can becrystallized without substantial alteration in their essential state,said ltration involving forming, washing, drying on,

and discharging from a rotating drum fllter surface a filter cake ofsolids in a continuous recurring cycle, the steps comprising dissolvingsaid mixture of fatty substances in a solvent comprising an aliphaticketone, chilling the solution to a filtering temperature such as toeffect crystallization from the solution of fatty constituents ofdesired relatively narrow solidiflcation point range, passing theresulting chilled mixture of solid and liquid phases to a continuousrotary drum vacuum filter with the filter drum about 40 to 50% submergedin the filtering mixture, maintaining the solid phase uniformlydispersed throughout the liquid phase and in the proportion of about 2to 6% by volume of the liquid phase in the mixture undergoing filtrationsuch that a filter cake is formed which is not less than about M; inchand not more than about 5/4 inch in thickness, separating liquid phaseas filtrate, washing said filter cake in situ with additional solvent atabout said filtering temperature to displace retained liquid phase,continuously discharging filtrate from said filter and continuouslydischarging washed filter cake from the filter substantially free fromfatty constituents solidifying below and above said filteringtemperature.

7. In the separation of solidiflable constituents from fatty substancescontained in fatty oil by continuous vacuum filtration in the presenceof a solvent liquid from which solidiable constituents can'becrystallized without substantial alteration in their essential state,said filtration involving forming, washing, drying on and dischargingfrom a rotating drum filter surface a filter cake of solids in acontinuous recurring cycle, the steps comprising chilling said fattysubstance mixed with said solvent to a filtering ternperature at whichcrystallization of desired solidifiable constituents occurs, forming atsaid filtering temperature a chilled mixture comprising a liquid phaseof non-crystallized fatty constituents dissolved in solvent and a solidphase of crystallized fatty constituents, said solid phase amounting toabout 2 to 6% by volume of the liquid phase at said filteringtemperature, passing a stream of said mixed phases, the solid phasebeing uniformly dispersed throughout the liquid phase, to a continuousrotary vacuum drum filter, separating liquid phase as filtrate andforming a filter cake of solid phase, washing said filter cake in situto displace retained liquid phase, continuouslv discharging filtratefrom said filter, and continuously discharging washed filter cake fromthe filter substantially free from fatty constituents solidifying eitherbelow or above said filtering temperature,

8. In the separation of solidiflable constituents from a mixture offatty substances contained in fatty oil by continuous vacuum filtrationin the presence of a solvent liquid from which solidiflable constituentscan be crystallized without substantial alteration in their essentialstate, said filtration involving forming, washing, drying on, anddischarging from a rotating drum filter surface a filter cake of solidsin a continuous recurring cycle, the steps comprising dissolving saidmixture of fatty substances in said solvent, chilling the solution to afiltering temperature such as to effect crystallization from thesolution of fatty constituents of desired relatively narrowsolidiflcation point range, passing the resulting chilled mixture ofsolid and liquid phases to a continuous rotary drum vacuum filter,maintaining the solid phase uniformly dispersed throughout the liquidphase in the proportion of about 2 to 6% by volil ume of the liquidphase in the mixture undergoing filtration such that afilter cake isformed which is not less than about Va inch and not more than about V4inch in thickness, separating liquid phase as nitrate, washing saidiilter cake in situ with additional solvent at about said filteringtemperature to displace retained liquid phase, continuously dischargingnitrate from said filter and continuously discharging Washed filter cakefrom the filter substantially free from fatty constituents solidifyingbelow and above said filtering temperature.

9. In the separation of solidifiabie constituents from a fatty oilmixture by continuous vacuum nltration in the presence of a solventliquid from which solidiiiable constituents can be crystallized withoutsubstantial alteration in their essential state, said filtrationinvolving forming, washing, drying on and discharging from a rotatingdrum filter surface a filter cake of solids in a continuous recurringcycle, the steps comprising chilling said fatty oil mixed with saidsolvent to a ltering temperature at which crystallization of desiredsolidiiable constituents occurs, forming at said illtering temperature amixture of fatty oil and said solvent liquid comprising a liquid phaseof fatty oil dissolved in solvent and a solid phase of crystallizedfatty constituents, said solid phase amounting to about 2 to 6% byvolume of the liquid phase at said filtering temperature, passing astream of said mixed phases, the solid phase being uniformly dispersedthroughout the liquid phase, to a continuous rotary vacuum drum filterwith the i'llter drum about 40 to 50% submerged in the filteringmixture, separating liquid phase as filtrate and forming a filter cakeof solid phase, washing said filter cake in situ to displace retainedliquid phase, continuously discharging filtrate from said filter, andcontinuously discharging washed filter cake from the filtersubstantially free from fatty constituents soiidifying below and abovesaid filtering temperature.

WILLIAM P. GEE.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 1,974,542 Parkhurst Sept. 25,1934 2,107,664 Gee Feb. 8, 1938 2,166,891 Gee July 18, 1939 2,228,040Voogt et ai. Jan. 7, 1941 2,288,441 Ewing June 30, 1942 2,248,668 GeeJuly 8, 1941 2,293,676 Myers et al Aug. 18, 1942 2,356,346 Packie et al.Aug. 22, 1944

